The function y = f(x) in a given range of the argument
x if there exists a positive number M such that for all values of x in
the range under consideration the inequality | f(x) | ≤ M will be fulfilled.
→ unbounded function.

The function y = f(x) in a given range of the argument
x if there is no number M such that for all values of x in
the range under consideration the inequality | f(x) | ≤ M will be fulfilled.
→ bounded function.